Consumer Cellular (MVNO with AT&T service) DOES allow tethering, but doesn't mention it on any of their plans. And it's free. You just have to call them and ask for it. They warn you that tethering can run up your data bill, and that's certainly true, but will enable it for you if you want it.
My data usage is mostly WiFi but I do need access for MBP occasionally. For me this is a great solution.
Research can't tell you everything. For example, it still hasn't told Apple what the iPad update cycle will be like. We now know it's longer than the iPhone cycle but not much else. I agree that some iPad Minis will turn up as iPhone 6 Plus sales instead. But then why keep the old Minis around ? Even back to the original ! There's something else going on here that we haven't yet understood.
I would expect that Square will update its iPad stand ("Square Stand") device to include NFC. They already have Lightning support and can connect to some external devices, so NFC is an obvious "want". But you might want something smaller, more like the card reader that Square (and others) offer. Square Reader will soon support chip cards but I haven't seen an announcement about NFC in the reader.
As I understand it, NFC is all the terminals need to support Apple Pay. So if they already have NFC then no update is necessary. I believe that there IS some software change needed in the merchant back-office system but that's software-only, not hardware. I expect that vendors of POS systems are providing those to their customers - the merchants.